Generally, exhaust gas from an internal combustion engine contains many kinds of noxious elements that cause air pollution, such as HC, CO, and NOx. Accordingly, it is required to eliminate the noxious elements before emitting the exhaust gas to the atmosphere.
A catalytic converter having a substrate is adapted to purify the exhaust gas containing the noxious elements. The substrate includes platinum (Pt) for deoxidizing carbon monoxide and hydrocarbons, and rhodium (Rh) for reducing nitrogenous compounds. The exhaust gas emitted from the engine passes through the catalytic converter and is catalyzed by contact with the catalysts.
The catalytic converter can catalyze the exhaust gas within a limited temperature range. Therefore, it is desirable to have a method of determining exhaust gas temperature at the catalytic converter inlet.
Conventionally, in order to determine the exhaust gas temperature at the catalytic converter inlet, a temperature sensor is provided to the catalytic converter for directly detecting the exhaust gas temperature. Alternatively, a method of predicting the exhaust gas temperature based on a plurality of variables representing the engine state is utilized.
In the case of a conventional method of predicting the exhaust gas temperature, the exhaust gas temperature at the catalytic converter inlet is determined utilizing a predetermined look-up table by applying an air charge rate and engine rpm as inputs. The obtained value is modified based on intake temperature and a time delay from the cylinder outlet to the catalytic converter inlet.
However, determining initial exhaust gas temperature is difficult when the engine is stopped and subsequently restarted. Furthermore, at a steady state, the influence of the exhaust pipe temperature on the exhaust gas temperature at the catalytic converter inlet is not considered. Accordingly, the exhaust gas temperature at the catalytic converter inlet can not be correctly predicted in both the initial state and the steady state.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known to a person skilled in the art.